In heat assisted magnetic recording (HAMR) technology, an FePt based recording medium may be heated to above its Curie temperature (Tc) using a laser. The laser generated heat may be guided to the medium using a near-field transducer (NFT) placed near the inductive write head. As the medium cools, writing is then carried out during the refreezing process. Because the bit transitions are determined by the thermal gradients, as opposed to just the write field gradients, much higher linear/track densities can be achievable with HAMR as opposed to previous magnetic recording technologies.
HAMR media performance, including the high linear/track densities, is largely determined by the thermal gradient which originates from proper heat sinking design in media stack. Ruthenium (Ru) which has relatively high thermal conductivity (kth) is a good material for the heatsink, but its hexagonal close-packed (HCP) crystal structure and rough surface make it difficult to establish epitaxial growth with cubic crystal structure based interlayers (for example, MgO) and above FePt recording films.